Means for starting gas turbine engines



June 6, 1967 L. s. SNELL 3,323,775

MEANS FOR STARTING GA$ TURBINE ENGINES Filed Feb. 18, 1966' 2 Sheets-Sheet 1 INVENTOR I- LEONARD STANLEY SNELL June 6, 1967 1.. s. SNELL 9 3 MEANS FUR STARTING GAS TURBINE ENGINES Filed Feb. 18, 1966 2 ShtSSh-8t 2 i --a LJF EQ ZL-AS ,9 Z i Q, 1o- ---1s U" 7/ 1 1 g; I iii-n :K FEQE.

INVENTORI" LEONARD STA NLEY SNELL.

United States Patent 3,323,775 MEANS FOR STARTING GAS TURBINE ENGINES Leonard Stanley Snell, Bristol, England, assignor to Bristol Siddeley Engines Limited, Bristol, England Filed Feb. 18, 1966, Ser. No. 528,532

Claims priority, application Great Britain, Feb. 20, 1965,

7,421/ 65 2 Claims. (Cl. 253-77) The invention relates to means for starting a gas turbine engine by impingement of a jet or jets of fluid on to part of a rotor of the engine to produce rotation thereof until the engine becomes self-sustaining in operation.

According to the invention, a rotor of a gas turbine engine includes a ring of axial flow blades, shrouded at their tips to define an annular radially-outer boundary of the gas passage through the blades and a plurality of circumferentially-spaced, radially-outwardly extending projections formed on the radially-outer surface of the blade tip shroud, each of the projections having an operative surface against which a fluid jet can impinge to exert a turning moment on the rotor.

Each blade or a plurality of adjacent blades may have a part-annular shroud portion at the tip or tips respectively, at least some of the shroud portions being provided with the aforesaid projections, alternatively, all the blade tips may be connected by a continuous annular shroud with the aforesaid projections. Alternatively, all the blade therearound.

According to a feature of the invention, the operative surface of each said projection is concave and forms an impulse bucket and may extend over substantially the whole axial length of the blade-tip shroud.

According to a further feature of the invention, a turbine including a rotor in accordance with any one of the three immediately preceding paragraphs also includes a casing containing the rotor and having a chamber therein arranged to receive a presurised fluid supply and nozzles communicating with the chamber, each nozzle being arranged in such manner that a jet of fluid from the nozzle outlet is directed towards the operative surface of a projection carried on the rotor, whereby on rotation of the rotor, the operative surfaces of all the projections will pass the nozzle out-lets in succession. The axis of each nozzle is preferably inclined to the rotor axis in two planes normal to one .another.

The invention also includes an axial flow blade having a part-annular shroud at its tip, the shroud having at least one radially-outwardly extending projection formed on the radially-outer surface of the shroud and the projection having an operative surface against which -a fluid jet can impinge to effect a turning moment on a rotor on which the blade is carried.

One embodiment of the invention as applied to the blades of an axial flow turbine is now described with reference to the accompanying drawings, in which:

FIGURE 1 is a fragmentary longitudinal section of the turbine casing and an adjacent shrouded turbine rotor blade;

FIGURE 2 is a plan view, to a larger scale, of a tip shroud of the turbine rotor blade, showing a projection thereon, and

FIGURE 3 is a section on the line 33 in FIGURE 1.

Referring to FIGURE 1, the turbine rotor comprises a disc, of which a part is shown at 2, carrying a plurality of axial flow turbine blades 3, the tips of which carry integral, part-annular shrouds 4, only one of which is shown. The shrouds 4 together form a ring around the blade tips and constitute a complete annulus defining the outer boundary of the gas flow passage through the blades.

Each blade 3 may carry its oWn individual shroud 4 or several adjacent blades 3 may carry a common partannular shroud.

Each shroud 4 has on its radially-outer surface an integral, radially-outwardly extending projection 5 extending over the whole axial length of the shroud and having a curved concave surface 6, forming an impulse bucket (see FIGURE 2), similar to a Pelton wheel bucket, against which jets of air are arranged to impinge.

For this purpose, an inner part 7 of the turbine casing 8 has a portion 9 extending around and in close proximity to the upstream ends of the projections 5 on the shrouds 4. Through this casing portion 9, there is a ring of holes forming nozzles 10, the inner ends 11 of which communicate with an annular chamber 12 formed by the inner casing part 7 and a spaced wall 13 which is provided at one position with an opening for an inlet connection 14 to a source of pressurised air.

The axes of the nozzles are so disposed that jets of pressurised air emitted from the outlet ends 15 thereof are directed towards and impinge successively against the concave surfaces 6 to produce rotation of the turbine rotor until such time that the engine becomes self-sustaining, after which the pressurised air supply to the chamber 12 is discontinued.

The air may be supplied from a starting turbine-compressor set or from a vessel containing compressed air. Instead of air, another compressed fluid may be employed to drive the buckets formed by the projections 5.

It will be seen from FIGURES 1 and 3 that the axis of a nozzle is inclined to that of the turbine rotor in two planes which are normal to one another.

The inner part 7 of the turbine casing also supports a ring of inlet nozzle vanes 16 and the downstream ends of concentric walls 17 and 18 of the combustion system.

Instead of the projections 5 being carried on partannular shrouds, a plurality of circumferentially-spaced projections 5 may be carried on a common complete annular shroud integral with all the blades 3.

By providing the projections 5 on the shrouds 4 at the tips of the blades, the following advantages result:

(a) The shrouds, which would otherwise be obstructive to jet impingement starting, are utilised to support the projections 5;

(b) The projections 5 have operative surfaces which may be designed to give eflicient starting;

(c) As the projections 5 are positioned radially beyond the shrouds 4, maximum turning moment will be effected during starting, and

(d) No additional starting means is necessary, thereby the weight of the engine is kept to a minimum value, this being an especially important feature for vertical lift engines.

What I claim as my invention and desire to secure by Letters Patent of the United States is:

1. A gas turbine having a rotor including a ring of axial flow blades shrouded at their tips to define an annular radially-outer boundary of the working fluid passage through the blades and -a plurality of circumferentiallyspaced, radially-outwardly extending projections on the radially-outer surface of the blade tip shroud, each of said projections having a concave operative surface forming an impulse bucket against which a starting fluid jet can impinge to exert a turning moment on the rotor, the turbine also including a casing defining a common duct containing said blades and said projections, said casing also having a chamber therein arranged to receive a pressurised supply of said starting fluid, means for providing said pressurised supply of starting fluid independently of said working fluid and nozzles communicating with said chamber, each said nozzle being so arranged that a jet {l of said starting fluid from the nozzle outlet is directed towards the operative surface of one of said projections carried on the rotor, whereby on rotation of said rotor, the operative surfaces of all said projections will pass said nozzle outlets in succession.

2. A gas turbine having a rotor including a ring of axial flow blades shrouded at their tips to define an annular radially-outer boundary of the Working fluid passage through the blades and a plurality of circumferentiallyspaced, radially-outwardly extending projections on the radially-outer surface of the blade tip shroud, each of said projections extending over substantially the whole axial length of the blade tip shroud and having a concave operative surface forming an impulse bucket against which a starting fluid jet can impinge to exert a turning moment on the rotor, the turbine also including a casing containing said rotor and having a chamber therein arranged to receive a pressurised supply of said starting fluid, means for providing said pressurised supply of starting fluid independently of said Working fluid and nozzles communicating with said chamber, each said nozzle being so arranged 5 will pass said nozzle outlets in succession.

References Cited UNITED STATES PATENTS 2,411,552 11/1946 New. 10 2,457,833 1/1949 Redding 6039.14

2,816,417 12/1957 Bloomberg. 2,971,333 2/1961 Mendelsohn et al. 6039.14 2,982,095 5/1961 Campbell 6039.14 3,085,396 4/1963 Kent et al. 6039.14 15 3,087,305 4/1963 He-rtzog 60--39.14

FOREIGN PATENTS 749,009 5/ 1956 Great Britain.

20 MARTIN P. SCHWADRON, Primary Examiner.

4 a that a jet of said starting fluid from the nozzle outlet is directed towards the operative surface of one ofsaid projections carried on the rotor, whereby on rotation of said rotor, the operative surfaces of all said projections EVERETTE A. POWELL, In, Examiner. 

1. A GAS TURBINE HAVING A ROTOR INCLUDING A RING OF AXIAL FLOW BLADES SHROUDED AT THEIR TIPS TO DEFINE AN ANNULAR RADIALLY-OUTER BOUNDARY OF THE WORKING FLUID PASSAGE THROUGH THE BLADES AND A PLURALITY OF CIRCUMFERENTIALLYSPACED, RADIALLY-OUTWARDLY EXTENDING PROJECTIONS ON THE RADIALLY-OUTER SURFACE OF THE BLADE TIP SHROUD, EACH OF SAID PROJECTIONS HAVING A CONCAVE OPERATIVE SURFACE FORMING AN IMPULSE BUCKET AGAINST WHICH A STARTING FLUID JET CAN IMPINGE TO EXERT A TURNING MOMENT ON THE ROTOR, THE TURBINE ALSO INCLUDING A CASING DEFINING A COMMON DUCT CONTAINING SAID BLADES AND SAID PROJECTIONS, SAID CASING ALSO HAVING A CHAMBER THEREIN ARRANGED TO RECEIVE A PRESSURISED SUPPLY OF SAID STARTING FLUID, MEANS FOR PROVIDING SAID PRESSURISED SUPPLY OF STARTING FLUID INDEPENDENTLY OF SAID WORKING FLUID AND NOZZLES COMMUNICATING WITH SAID CHAMBER, EACH SAID NOZZLE BEING SO ARRANGED THAT A JET OF SAID STARTING FLUID FROM THE NOZZLE OUTLET IS DIRECTED TOWARDS THE OPERATIVE SURFACE OF ONE OF SAID PROJECTIONS CARRIED ON THE ROTOR, WHEREBY ON ROTATION OF SAID ROTOR, THE OPERATIVE SURFACES OF ALL SAID PROJECTIONS WILL PASS SAID NOZZLE OUTLETS IN SUCCESSION. 